The invention relates to a method for preparing a coating resistant to contact corrosion on the surface of titanium alloy, which comprises the following steps: 1. carrying out degreasing and derusting to a titanium alloy part; 2. carrying out etching treatment on the titanium alloy part; 3. carrying out surface activation treatment on the titanium alloy part; 4. preheating the titanium alloy part in an atmosphere protection furnace; 5. immersing the preheated titanium alloy part in plating solution; and 6. carrying out diffusion treatment on the immersion-plated titanium alloy part in a vacuum furnace whereby atoms at the interface diffuse to form a diffusion layer on a substrate and thus form a plating diffusion composite layer on the surface of the titanium alloy part. The part treated by the method completely solves the problem of contact corrosion of titanium alloy contacting with aluminum alloy and steel material.